5-Thio-D-glucose with radioactive sulfur will be followed in the glycolytic pathway to determine the manner of sulfur elimination. An examination will be made of the effect of 5-thio-D-glucose on purified rat liver glucokinase and rat brain hexokinase with the additional view to see if 5-thio-D-glucose 6-phosphate can act as a feedback inhibitor to rat brain hexokinase. 5-Thio-D fructose phosphorylation will be examined using rat liver hexokinase and the 6-phosphate will be examined as a substrate and/or inhibitor to rat liver phosophofructokinase. Some further examination will be made of the unusual stimulation of glycogen synthetase activity by UDPTG (the 5-thio-D-glucose analog).